Introduction to the Accelerometer¶
The accelerometer is a mechanical sensor that measures acceleration in the three axis X, Y, Z. When you tilt your phone and the screen changes to widescreen, it's done because of an accelerometer. This sensor is commonly used in electronics in general, here's a short overview.
How it works¶
Acceleration is measured through displacement of a body with a certain mass connected to a spring (that's why the accelerometer is a mechanical sensor). The mass has "fingers" acting as movable capacitance plates and these are close to stationary capacitance plates. The force required to move the spring mass a certain distance can be easily converted to capacitance and that's how you get analog input from the sensor.
This is how measuring acceleration works in one axis. The sensor has a total of three: X, Y, Z.
Accelerometer axis orientation¶
The accelerometer has its axis defined from factory, ergo the way the sensor is assembled has an effect on the orientation of the sensors. This is the orientation in our devices:
Things the accelerometer can measure and report¶
Any movement in general can be reported as long as acceleration is detected.
Please note the accelerometer often doesn't pick up smooth movement of e.g. big office doors as the acceleration is too weak to trigger an alert. In simple use cases, accelerometer can be substituted with the magnetometer which doesn't require a certain acceleration to pick up orientation change.
Orientation changes through several firmware features.
Vibration monitoring over time.
Raw acceleration data in mg.
The sensitivity of the sensor is by default the same in all three axis, but can be customized so you can have e.g. Z axis more sensitive than the other two.
Common use cases¶
- Tracking goods being delivered
- Tracking stolen items
- Tracking luggage around the world
- Monitoring the usage of engines and other vibrating machine parts
- Monitoring that objects (poles, trees, etc) stay in their place via tilt
- Monitoring that objects (lids, covers, dust bins etc) return to their original place
- Measuring movement time of objects
- Reporting when objects fall down
- Reporting impact on objects such as doors or packages
- Monitoring occupancy of chairs
- Earthquake detection and status of building integrity
- And others...